THEY say that beauty is only skin deep – and in the eye of the beholder.

But it seems that your race could at least give you a little head start – or hold you back – in the quest to turn the heads of the opposite sex.

Welsh researchers claim to have discovered a reason behind marked differences in patterns of mixed marriages – and its all rooted in the perceived attractiveness of the face.

Scientists from Cardiff University found differences in perception of attractiveness in different races, which could account for significant differences in which races tend to marry each other in the UK.

The team examined the preferences of a research group of students rating faces of the opposite sex and, using a mathematical formula devised from the results, found that it correlated closely with statistical trends of mixed-race marriages in the UK.

Black men in the study were found to be the most attractive to females based on facial characteristics, while Asian women were perceived to be most facially attractive to men.

It could account for the reason why singer Seal first attracted Heidi Klum, or indeed why Yoko Ono first turned the head of John Lennon.

The Cardiff team is the one that was behind previous research which claimed that mixed-race people were perceived to be more attractive than either black or white people.

Government data shows a marked difference in patterns of interracial marriage, with around one-and-a-half times more black men marrying white women in the UK and the US, than black women marrying white men.

More white men have also been found to marry east Asian women east Asian men marrying white women.

Dr Michael Lewis, from Cardiff University’s School of Psychology and lead of the study, said that existing explanations of interracial marriage based on racial, economic or social factors were unable to explain the asymmetries.

The students, aged between 18 and 30, were also of these three ethnicities.

Black male faces, on average, were rated as most attractive, followed by white faces and then Asian, while – for females – Asian faces were seen as the most attractive on average, followed by white and then black faces.

“It is no coincidence that groups perceived as being more attractive – black males and Asian females – feature more often in mixed-race marriages than their opposite-sex counterparts,” said Dr Lewis.

Dr Lewis was also behind research in 2010 which revealed that mixed-race people were perceived to be more attractive than white or black people, after one of the largest studies of its kind.

The results, based on a similar experiment template based on a sample of 1,025 black, white and mixed-race faces, appeared to confirm that people whose genetic backgrounds are more diverse are, on average, perceived as more attractive than those whose backgrounds are less diverse.

The team was able to say that – combining the results of the study and comparing to the share of the population of mixed-race people – that they were “over-represented” at the top of professions in society.

But in the latest research, academics devised and tested a mathematical formula of marriage behaviour on the back of the attractiveness data from the student sample, which produced the same patterns of mixed-race marriages found in government records.

The model also suggested that those taking part in mixed-race marriages are, on average, more attractive than those in same-race marriages.

“It will come as no surprise to many that facial attractiveness makes up part of the decision of who we marry, but previously this factor has not featured much in scientific models of marriage,” said Dr Lewis.

“Instead, more measurable features such as wealth, fertility or racial status have been considered to be more important.

“This new explanation accounts for the same patterns observed in the marriage data but does not require there to be differences in racial status between black and white people, only differences in perceived attractiveness.”